"And of those hundred billion suns, large and small- how many shine upon worlds that carry life? Perhaps most of them, for matter has the same properties throughout the universe. We know that life arose independently on Earth and Mars. we believe that it arises automatically on all worlds that are not too hot or cold, that have the common elements of oxygen and carbon and hydrogen, and that are bathed by sunlight for a few billion years.

  "Yet even if life is common, intelligence may be rare; in the long story of Earth, it has evolved only once. Nevertheless, there may be millions of advanced cultures scattered throughout the Galaxy-but they will be separated by gulfs that light itself takes years to span."

  Two arrows appeared, aimed at stars so close together in the sparsely populated outer arms of the Galaxy that they seemed to be neighbors.

  "If this was our Sun, and we sent a radio signal to a planet circling this nearby one, it would take a thousand years for the reply.... Or, to put it in another way, we might expect an answer now, if the message left our world around the birth of Christ.... And this would be a conversation with one of the closest of our galactic neighbors.

  "Yet even if it takes thousands of years to travel from star to star, a really advanced race might attempt the feat. It could send robot ships exploring for it-as Man has already sent his robots ahead of him to explore the Moon and planets."

  There were shots of ungainly space probes-some familiar, others obviously imaginary-drifting across the stars, peering down at passing worlds with their television eyes.

  "Or they might build huge space arks-mobile planetoids which could travel between the stars for centuries, while generation after generation lived and died upon them....

  "Or they might hibernate, or be frozen in the changeless sleep of suspended animation, to be awakened by robots when their age-long journey neared its end....

  "Even these are not the only possibilities. A very advanced race might be able to build ships that could attain almost the speed of light. According to Einstein, no material object can travel faster than this; it is the natural built-in speed limit of our universe. However, as we approach this speed, time itself appears to slow down. A space traveler might fly to a distant star in what, to him, appeared to be only a few months-or even a few hours.

  "But only to him. When he returned from his destination, he would find that years or centuries had passed, that all his friends were dead, and, perhaps, that his very civilization had vanished. That would be the price of stellar exploration-trading Time for Space, with no possibility of refund. Yet the price might be attractive, to creatures whose lives are much longer than ours.

  "Finally-perhaps Einstein's theory, like so many theories in the past, does not tell the whole truth. There may be subtle ways of circumventing it, and so exceeding the speed of light. Perhaps there are roads through the universe which we have not yet discovered-shortcuts through higher dimensions. 'Wormholes in Space,' some mathematicians have called them; one might step through such a hole-and reappear instantaneously, a thousand light-years away.

  "But even if this is true-and most scientists think it pure fantasy-the exploration of the universe will still require unimaginable ages. There are more suns in the whole of space than there are grains of sand on all the shores of Earth; and on any one of those grains, there may be civilizations that will make us look like primitive, ignorant savages.

  "What will we say to the peoples of such worlds, when at last we meet? And what will they say to us?"

  "Thank you, Victor," said Manning when the screen blanked out and the red light in the dubbing room went off. "I knew you'd do it. Don't worry about the fluffs- we'll fix them. Anyway-what did you think of it?"

  "Not bad-not bad. But I wish you hadn't put in that nonsense at the end."

  "Eh? What nonsense?"

  "Higher dimensions, wormholes in space, and all that rubbish. That's not science; it's not even good science fiction. It's pure fantasy."

  "Well, that's exactly what the script said "

  "Then why bring it in? Whose bright idea was it?"

  "One Dr. Heywood Floyd's, if you want to know. I suggest you take it up with him."

  Kaminski really meant it, but somehow the matter slipped his mind. There was so much work to do, so much to learn, that it was months before he thought of it again.

  And then it was far, far too late.

  ANCESTRAL VOICES

  The ape-man stood on a low, rocky hill, grasping a pointed stone and looking out across a dusty African plain. Overhead, the sky was cloudless, and a hot sun baked the yellowing grass of the savannah and the stunted trees which provided the only shade. In the middle distance, a small herd of gazelles was browsing, watched intently by a saber-toothed tiger crouching in the scrub.

  There were more ape-men-about a dozen of them- scattered over the crown of the little hill. Propped up against a large boulder, one female was nursing her baby; not far away, two juveniles were quarreling over a hunk of meat-all that was left of some small dismembered animal. One bent and gray-haired male was trying to suck the marrow from a cracked bone; another was curled up asleep; two females were grooming each other for lice; and yet another male was hunting through a pile of dried bones in search of future weapons.

  "It's a beautiful model," said Bowman at last, when he and his two companions had looked their fill.

  "Thank you," answered the curator of Anthropology. "It's as accurate as humanly possible several years of work went into it."

  Dr. Anna Brailsford was a striking, dark-haired woman in her early forties, who seemed much too vivacious to have devoted her life to fossils. Though she was a famous explorer and veteran of many expeditions, she had lost none of her femininity; it was hard to believe that she was one of the world's leading authorities on early Man.

  "So these," said Phillip Goode, Bowman's understudy, "are the characters the pyramid-makers would have met, if they landed on Earth three million years ago?"

  "Not necessarily. It depends on the thoroughness of their investigation. Australopithecus was probably not very common; he might easily have been overlooked among the elephants and giraffes and other more conspicuous animals. In fact, he wasn't even the most impressive of the primates. To a casual visitor, he might have seemed just another ape."

  It was rather difficult, thought Bowman, to take so detached a view. His great-to-the-hundred- thousandth grandfather was not a very prepossessing sight, but there was a wistful sadness about the hairy, no-longer-quite animal face staring at him through the glass of the diorama. He was not ashamed to admit kinship with his remote ancestor across the unimaginable ages that sundered them. "I rather doubt," he said dryly, "that creatures landing on Earth back in the Pleistocene would have been casual visitors. And this is one of the things we wanted to discuss with you-their motivations."

  "Well, I can only tell you how I'd behave, in the same circumstances. I'd note that Earth was teeming with advanced life forms, but that none of them had developed high intelligence. However, I'd probably guess-I might even be able to predict, with the knowledge I'd undoubtedly have-that intelligence would arise in a few million years.

  "So I'd leave behind some intelligence monitors-or, better still, civilization detectors. I might put some of them on Earth, though I'd realize that they would probably be destroyed or buried before they had a chance to operate. But the Moon would be an ideal spot for such a device especially if I was only interested in civilizations that had reached the space-faring stage. Any culture still planet-bound might be too primitive to concern me."

  "So you're in favor of the fire-alarm theory, as we call it, to explain TMA-1?"

  "Yes-it seems very plausible. But perhaps it's too plausible. Human motivations vary so much that any attempt to analyze wholly alien behavior must be pure guesswork."

  "But guesswork is all we have to go on for the present. We're trying to think of every possibility that may arise, when and if we do catch up with the creatures who built TMA-1."


  Bowman pointed to the frozen tableau of his ancestors.

  "Look how far we've progressed since then! Yet after that same three million years, where will the pyramid makers be? I don't mind admitting it-the thought sometimes scares me."

  "It scares me. But remember, progress is never uniform; even after three million years, they may not be incomprehensibly far ahead of us. Perhaps there's a plateau for intelligence that can't be exceeded. They may already have reached it when they visited the Moon. After all, it has yet to be proved that intelligence has real survival value."

  "I can't accept that!" protested Bowman. "Surely, our intelligence has made us what we are-the most successful animals on the planet!"

  "As an anthropologist, I'm naturally biased in favor of Man. From the short-term point of view, intelligence has undoubtedly been an advantage. But what about geological time-and how do you define a 'successful' species? My friend the curator of reptiles keeps reminding me that the dinosaurs flourished for more than a hundred million years. And their I.Q.'s were distinctly minimal."

  "Well, where are they now? I don't see any around today."

  "True-but you can't call a hundred-million-year reign a failure; it's a thousand times as long as Homo sapiens has existed. There may be an optimum level of intelligence, and perhaps we've already exceeded it. Our brains may be too big-dooming us as Triceratops was doomed by his armor. He overspecialized in horns and spikes and plates; we overspecialized in cerebral cortex. The end result may be the same."

  "So you believe that as soon as a species reaches more than a certain level of intelligence, it is heading for extinction?"

  "I don't state it as a fact, I'm merely pointing out the possibilities. There's no reason to assume that the universe has the slightest interest in intelligence-or even in life. Both may be random, accidental by-products of its operations, like the beautiful patterns on a butterfly's wing. The insect would fly just as well without them; our species might survive as long as-oh, the sharks, which haven't changed much in a couple of hundred million years-if we were a little less clever. Look at the daily newspapers, and the history of the whole twentieth century."

  Dr. Brailsford smiled at her obviously disapproving audience.

  "No-I'm not a pessimist," she said, answering their unspoken accusation. "Just a realist, who knows that only a tiny fraction of the species that have lived on this planet have any descendants today. And because I am a realist, perhaps I understand the importance of your project better than you do."

  "Go on, please."

  "The creatures who built the pyramid-how far ahead of us would you say they were from the technical viewpoint?"

  "Probably no more than a hundred years, at our present rate of progress."

  "Exactly. Now suppose that they are still in existence, even if they've made little progress during the three million years since they visited the Moon. Don't you see-this will be the first definite proof that intelligence does have real survival value. That will be very reassuring."

  "Quite frankly, doctor," said Goode, "I don't need any reassurance. Even if intelligence has limited survival value, it has a good deal of comfort value. I wouldn't change places with them." He jerked his thumb toward the tableau of ape-men.

  The anthropologist joined in the laughter; then she became serious again.

  "There's another possibility, though-and that's cultural shock. If they are too advanced, and we come into contact with them, we may not be able to survive the impact psychologically. As Jung put it, half a century ago, we might find all our aspirations so outmoded as to leave us completely paralyzed. He used a rather striking phrase- we might find ourselves 'without dreams.' Like the Atlanteans, you know-Herodotus said that they never dreamed. I always thought that made them peculiarly inhuman-and pitiable."

  "I don't believe in cultural shock," said Hunter. "After all, we expect to meet a very advanced society. It wouldn't be such an overwhelming surprise to us as-well, as it would be to him, if he was suddenly dumped here in Manhattan."

  "I think you are too-optimistic," answered Dr. Brailsford; Bowman guessed that she had been tempted to use the word "naive." "On our planet, societies only a few generations apart culturally have proved to be incompatible."

  "Perhaps our Pleistocene astronauts were aware of the danger-perhaps that's why they've left us alone, all these years."

  "Have they?" said the anthropologist. "I wonder. If you'd like to come to my office now, I've something to show you."

  They walked out of the Leakey Memorial Exhibit, through the great, cathedral-like halls of the museum. From time to time Bowman was recognized by other visitors, and several eager youngsters rushed up for his autograph. Goode and Hunter were not asked for theirs, but they were accustomed to this; Goode was fond of quoting, a little ironically, Milton's line "They also serve who only stand and wait."

  Bowman's relationship with his two understudies was, on the whole, excellent-which was not surprising, for their intellectual and psychological profiles had been matched with great care. They were colleagues, not competitors, and they were often able to act as his alter egos, reporting back to him after missions and trips which he was too busy to make. Of course, each hoped that he would be the one finally selected, but they served Bowman loyally and with the minimum of friction. They had had disagreements, but never a serious quarrel-and so it had been with the other five trios. The psychologists had done their work well; but by this time, they had had plenty of practice.

  Every time he entered a place like the Natural History Museum, Bowman was overwhelmed by the infinite variety of life produced by evolution on a single world, this one planet Earth. As he walked past the great displays with their panoramas of scenes from other times and other continents, he realized again the sheer foolishness of the question he was so often asked about the builders of the pyramid: "What do you think they looked like?"

  Even if one were given every relevant fact about Earth's climate, geography, atmosphere, and chemical composition, who could have predicted the elephant, the whale, the giraffe, the giant squid, the duck-billed platypus-or Man himself? How infinitely more impossible it was, therefore, to make sensible guesses about the inhabitants of a totally unknown, and perhaps quite alien, planet! Yet it was equally impossible to stop trying....

  Dr. Brailsford's office was that of any museum curator- piled high with books, reports, journals from other institutions, exhibits being packed and unpacked, and hundreds of small drawers which covered two whole walls. On her desk were several skulls; she picked up one and said: "Here is the gentleman we have been talking about; not much of a forehead yet, but he's taken the first step toward us. And I mean first steps; even today, none of the other anthropoids are good walkers."

  She placed the skull reverently back into its bed of cotton wool, then began ruffling through the folders drawings, maps, and photographs on her crowded desk. Presently she dug out a large book,* opened it at a marker, and handed it over to her visitors.

  *The Search For the Tassili Frescoes, Henn Lhote

  "My god!" said Hunter. "What the devil is that?"

  "That" was a line drawing of a looming, roughly anthropomorphic figure, shown from the waist up. The head appeared to be covered by some kind of helmet, in the center of which was a large, Cyclopean eye. Another, smaller eye was tucked away in one corner of the helmet there were no other features, and by no possible distortion or artistic license could it be converted into a human face.

  "Thought-provoking, isn't it? It's a Paleolithic cave painting, found in the Sahara half a century ago-back in 1959. And it made such an impression on the discoverers that, believe it or not, they christened it the 'Great Martian God."

  "How old is it?"

  "About ten thousand years. Not very old compared with your TMA-1-but ancient enough by human standards."

  There was a long and profound silence while the three astronauts studied the painting. Then Hunter asked: "Do you really think it's a record of a meeting with e
xtraterrestrials?"

  "Frankly, no. It's probably a medicine man or witch doctor wearing some peculiar hairdress. I should have mentioned that it's extremely large-about eighteen feet high-so the artist obviously considered it quite important."

  "Or it was something that made a big impression on him. I guess a spacesuit back in the Stone Age would create a sensation."

  "Not necessarily, you should see a New Guinea devildancer in full regalia. But I think we can draw a lesson from this; just suppose it was a visitor from space, wearing some kind of protective suit. Granted that, I think you'll agree that the Stone Age artist did a fine job of recording something utterly incomprehensible, and beyond the farthest limits of his own culture. Could you do as well, if you encountered a supercivilization?"

  "Perhaps not-but at least we have cameras."

  "Even in photographs, you can only recognize things you already know. The shapes and colors of a really advanced civilization might be so strange that we might go mad trying to interpret them. Its time scale, too, might be incompatible with ours-faster, for example. Suppose you put Australopithecus in a car and drove him at high speed down Broadway one night. What sense would he make of it?"